Beginning in the 1920s, Louis Armstrong was the undisputed fountainhead of American jazz. With his bright, clear trumpet and his ebullient, gravelly voice, he more or less defined how jazz is meant to played and sung.

Everything he did is of interest to musicians and scholars, and few American lives have been better documented. But until last week, little was known about a performance he recorded in Washington five months before he died in 1971.

At a news conference this month at the site of Armstrong's original recording at the National Press Club, the music he made more than 40 years ago finally was made available to the public. The original album, “Red Beans and Rice-ly Yours: Satchmo at the National Press Club,” had a limited pressing of 300 vinyl LPs. The new release will be available as a compact disc, on iTunes and from other digital sources. It marks one of Armstrong's final performances on trumpet.

“I've always lamented that it was never commercially available,” says Ricky Riccardi, an archivist for the Louis Armstrong House Museum in New York and author of “What a Wonderful World: The Magic of Louis Armstrong's Later Years.” “He changed music with his voice and his horn and pretty much created the vocabulary of American music. Knowing that he was giving it his all onstage for one of the last times in his career is a testament to this great genius of American music.”

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The title of the album derives from how Armstrong often signed letters and autographs. (At one point in his performance, he refers to the “good Creole food” at the Press Club dinner; recipes for more than 30 dishes are included with the disc.)

Before his memorable appearance at the Press Club, Armstrong had been in poor health for more than two years. Doctors had told him to stop playing the trumpet, but he kept practicing at his home in Queens. By the late summer of 1970, Armstrong had regained enough strength to blow his horn in public again.

He appeared in Las Vegas, on a few television shows and in a British documentary before coming to Washington on Jan. 29, 1971. He was the featured performer at a celebratory dinner honoring a fellow Louisianan, Vernon Louviere, who was being inaugurated as president of the Press Club.

Louviere, a one-time newspaper reporter who later worked for Nation's Business magazine, “loved all things related to New Orleans,” his daughter, Amy Louviere, says. He took his oath of office as Press Club president by placing his hand on a bottle of Tabasco sauce.

Louviere's four children attended the black-tie gala with their parents and got to meet Armstrong.

“I remember he was very full of life,” recalls Amy Louviere, who was 11 at the time. “He was trying to get me to smile for a picture and was joking around. The whole evening seemed overwhelming. I heard years later that people called that the best inaugural ball they ever had.”

Celebrities present that night included singer-actress Diahann Carroll, Cajun TV chef Justin Wilson and British talk-show host David Frost, who was master of ceremonies. An engineer from CBS recorded the evening's events, including Louviere's swearing-in, which is included on the re-released album.

The original album — filled out with a later performance by a band led by Armstrong's longtime musical partner, trombonist Tyree Glenn — was distributed only to people who attended the event. Decades later, several Press Club members, including one-time music producer Dan Doyle and the club's executive director, William McCarren, led the effort to put the recording back in circulation.

It took years to iron out the legal rights to the recording, which is being released by the Smithsonian Institution's Folkways recording label.

“There was a realization that we had a little jewel of his life's work,” says D.A. Sonneborn, associate director of Smithsonian Folkways.

During a 20-minute performance at the Press Club, Armstrong and his band performed five numbers, and he played trumpet only on the first two, “When It's Sleepy Time Down South” and “Hello, Dolly!”

“It's such an entertaining performance,” says Riccardi, one of the country's leading Armstrong historians. “I love that ‘Hello Dolly!' solo. On this recording, it's a completely new improvised solo.”

Armstrong told an off-color joke at one point and sang three other tunes, “Rockin' Chair,” “Boy From New Orleans” and an abbreviated version of “Mack the Knife.”

On July 6, 1971, a little more than five months after his Press Club appearance, Armstrong died at age 69.